This large, beautiful, geothermal pool is just one of hundreds of geysers, hot springs, mud pots, steam vents and other features at Yellowstone National Park that is not Old Faithful.
Daniel Terdiman/CNET

YELLOWSTONE NATIONAL PARK--If there's any doubt that more visitors to this treasure of nature check out Old Faithful than anything else, all you need to do is compare the size of the world-famous geyser's parking lot to that of any other place in the park.

But while Old Faithful may be synonymous with Yellowstone geothermal activity in most visitors' minds, it is, in fact, just one of hundreds of geysers, hot pools, mud pots, hot springs, and steam vents scattered throughout the park. And on Road Trip 2009, I set out to explore the lesser-known members of the geothermal club in order to give them a little much-deserved exposure.

Even with that goal in mind, I had no idea just how many different geothermal features Yellowstone has. For me, it was education on the fly, and, it turned out, I didn't have nearly enough time to see, and experience it all. In fact, while I did--how could I not?--save some time to watch Old Faithful do its thing (see video below), I ran out of time before getting to visit some of the more incredible hot pools on the list.

But I did get to see dozens of the beautiful pools, springs, pots and vents, and it was well worth the time I spent doing so, even though that time came at the expense of any opportunity to explore wildlife, waterfalls, meadows, lakes, or any of Yellowstone's myriad other attractions. For me, my visit was all geothermal, all the time.

In fact, Yellowstone has the largest geothermal area in the world, fully half of the planet's entire collection, according to the National Park Service.

"Yellowstone holds the planet's most diverse and intact collection of geysers, hot springs, mud pots, and fumaroles," according to the National Park Service. "Its more than 300 geysers make up two-thirds of all those found on earth. Combine this with more than 10,000 thermal features comprised of brilliantly colored hot springs, bubbling mud pots and steaming fumaroles, and you have a place like no other...Yellowstone's vast collection of thermal features provides a constant reminder of the park's recent volcanic past. Indeed, the caldera provides the setting that allows such features as Old Faithful to exist and to exist in such great concentrations."

Clearly, as a marketing vehicle, Old Faithful is as good as gold. But it's just one geyser, albeit a dependable, and large, one. To me, given that you have to stay well back from it, unlike many other geothermal features in the park, there's something very Disneyland about it. The real substance is elsewhere.

To begin with, I started my visit was a trip to an area called the Artists' Paintpots. This was a good primer, as it featured mud pots that can erupt up to 15 feet in the air. Unfortunately, I didn't get to see quite that level of airborne mud, but the geothermal features there were a nice way to start the day and get a sense of what was in store.

Four kinds of geothermal

Yellowstone features four main kinds of geothermal activity. They are hot springs, mud pots, geysers, and steam vents.

According to the National Park Service, "Hot springs are the most common geothermal feature in Yellowstone. Their underground plumbing consists of unconstricted chambers of varying sizes. Water, which has been superheated far underground, rises along tiny cracks, flows into larger channels and eventually reaches the earth's surface.

"Unlike geysers, water convection is continuous within hot spring pools. Hot surface water sinks while hotter, superheated water continues to rise. This circulation keeps water below the temperature needed to begin the chain reaction leading to an eruption."

Among the more beautiful examples are the Silex Spring, the Emerald Spring, the Green Dragon Spring, and the Cistern Spring. And those were just the ones I saw.

Interestingly, while geothermal change is often measured in the thousands of years, Yellowstone is home to the kinds of change that on a geological time scale would seem like mere seconds.

For example, the Red Spouter, on Yellowstone's Fountain Paint Pot Trail, didn't even exist prior to the Hebgen Lake Earthquake of 1959. But since that horrific 7.5 quake, which killed 28 people, Red Spouter has become a Yellowstone favorite, exhibiting "the behavior of all four thermal features," according to the National Park Service. "In the spring and early summer, its pools splash muddy water that sometimes has a red tone. Later in the summer and fall, when the water table is lower, Red Spouter becomes a hissing fumarole."

The last of the four styles of geothermal activity, fumaroles, or steam vents, "are hot springs without enough water to erupt or overflow," according to the National Park Service. "The small amount of water boils away, leaving only steam and other gases to escape...Steam vents usually exist on higher ground above other geothermal features."

In the park's geothermal rich Norris Geyser Basin, a small spring called Mystic Spring is reflective of even more recent change. According to a park ranger I met at the spring, a small earthquake just weeks ago has changed its behavior (see video below). The ranger said it may even have taken days for the quake--if that's indeed what was responsible--to effect Mystic Spring's new activity.

One thing Old Faithful makes clear, of course, is that it's a lot of fun to watch a big geyser go off. And at Yellowstone, there are plenty of places to watch that happen. To be sure, few go off as regularly or as predictably as Old Faithful, but some can still be counted on. For example, Steamboat Geyser, in the Norris Geyser Basin, was going off constantly. It was always producing huge amounts of steam, and every couple of minutes, spouts of boiling water would shoot in the air.

The same was true for Clepsydra Geyser, on the Fountain Paint Pot Trail. And, too, for White Dome Geyser, on Firehole Lake Drive.

"Geysers are hot springs that periodically eject boiling water and steam into the air," reads a National Park Service sign. "Most geysers are unpredictable. Some, like Old Faithful, display patterns of activity...A narrow zone, or constriction, and boiling water are necessary for a hot spring to erupt as a geyser. The constriction keeps water within the system from circulating to the surface for cooling. Eruptions occur as a chain reaction: Water, held within the geyser's plumbing, becomes superheated--heated beyond boiling--and rapidly expands in volume as it changes into steam; then steam bubbles force themselves--and the water above--past the constriction and up into the air."

Perhaps some of the most fun features, though, are the mud pots, or paint pots, as they're known throughout the park. These are springs that look like big cauldrons of boiling mud, often spitting mud in the air, but more likely just bubbling away, sounding like something is cooking.

They can be quite stunning to look at (see video below) and, in the case of the Artists' Paint pots and the Fountain Paint Pot Trail, are well-recognized places to visit within the park.

A mud pot, according to the National Park Service, is a hot spring "containing a relatively small amount of acid water. Acid breaks down the surrounding rock into clay, which mixes into the water. Mud consistency ranges from thick to thin, depending on the amount of water present. Abundant surface water in winter and spring thins the mud, creating a soupier mud pot. During the drier months of summer and autumn, mud pots often become thicker and sometimes dry up altogether."

By my count, there are at least 13 different geothermal areas in Yellowstone, and there's no way anyone could comfortably visit them all in one day, at least not with the goal of exploring them at a leisurely pace allowing for actually learning something.

Yet, with that many scattered throughout the park, one has to be careful with the clock. The hot springs, geysers, steam vents and mud pots are gorgeous, mysterious, dangerous, and a serious time suck. And I highly recommend visiting them. Sure, go see Old Faithful, but just as a single stop during your time there.

What I don't recommend, partly because it's illegal, but mostly because it's just dumb and reckless, is throwing anything into any of the springs, pools, pots or vents. They are irreplaceable, and extremely sensitive to foreign matter. Yet every year, Yellowstone visitors do just that, damaging the geothermal features, in some cases, permanently. The Park Service has posted signs warning against such behavior, but not in enough places. My message to you: go visit Yellowstone's geothermal wonderland, but keep your coins in your pocket.

For the next week, Geek Gestalt will be on Road Trip 2009. After driving more than 12,000 miles in the Pacific Northwest, the Southwest and the Southeast over the last three years, I'll be writing about and photographing the best in technology, science, military, nature, aviation and more in Wyoming and Colorado. If you have a suggestion for someplace to visit, drop me a line. And in the meantime, join the Road Trip 2009 Facebook page and follow my Twitter feed.